This ability is insane, even with the rank III priest bug left out.
This gives you and you allies 12 hps, make it on par with inner grace since its area heal, and it buff your AND other general priests to insane levels.
Now, a priest can heal every 5 secs, but it applies a debuff to a target after it healed it so that it can only be healed after 8 secs again. This means for invididual healing you get a big hp boost every 8 secs, but in teams this is off the scale.
The priest bug makes your rank III priests heal their target for 30 percent. Consider a Sedna with HW and rank three priests and an assasin, lets say UB. If he the UB can get 6k, which is easily obtained by lvl 10, the priests heal more than Sedna's regular heal AND can heal every 5 secs(2k health). Don't even get me stared what stacked generals with super powered priest can do.
I'm a terrible Sedna and this was just a casual game that I played, but with HW and super hp stacking, I could just walk through the enemy base or survive three man ganks or walk to the portal get ganked kill both the enemy DG's(seperatly though) cap the portal and walk out. This wasen't a very serious game so I noone was really playing their best, but still the only way I got killed was an area stun that stunned my priests and me inside the enemy base while I got ganked by Oak and Erebus. Had a good Sedna player in a serious game used this...
It's not unbeatable, as shown by the mass charm ganks, and obviously if they fix the priest bug it will be a lot less, but damn 2k every 5 secs?!